[DERBY-4544] Referencing streaming CLOBs in (some) generated column clauses fails

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.5.3.0, 10.6.1.0
• Fix Version/s: 10.5.3.2, 10.6.2.4, 10.7.1.4, 10.8.1.2, 10.9.1.0
• Component/s: SQL
• Labels: CLOB derby_triage10_8
• Urgency: Low
• Issue & fix info: Patch Available, Repro attached
• Bug behavior facts: Data corruption
• Assignee: Richard N. Hillegas
• Reporter: Kristian Waagan
• Created: 10/Feb/10 12:45
• Updated: 17/Jun/13 09:19
• Resolved: 26/Mar/12 17:38

Description

Referencing a CLOB represented as a stream in generated columns can lead to data corruption or that the query fails.

For instance, with 10.5:
create table t (id int, myclob clob, clen generated always as (length(myclob)));

1. Insert CLOB using the streaming APIs (setCharacterStream).
   The exception 'java.lang.ClassCastException: org.apache.derby.iapi.types.ReaderToUTF8Stream cannot be cast to org.apache.derby.iapi.types.Resetable'

On trunk the same query results in data corruption, and this isn't detected before the value is read back from store.

Workaround:
Don't use the streaming APIs when using CLOBs in generated columns. This increases the memory footprint, and may not feasible for large CLOBs.

FYI, BLOB deals with this by materializing the value, which effectively equals to using the workaround mentioned above.

Issue Links

• is related to: DERBY-4754 SQLClob.getObject() should always return a java.sql.Clob
• is required by: DERBY-5654 10.5 Backport issue (2012)